So there is no difference between actor and actress, that is, in Turkish the single world oyuncu is valid for either males or females? Is this true of all professions (doctors, teachers, lawyers, presidents, etc?)

Especially among professional theater people, "actor" is often used in place of "actress" nowadays. A lot of feminine endings for occupations have gone out of favor in English, at least in America. You would never call a female poet a "poetess," for example, and airline stewards and stewardesses are generally called "flight attendants."